What can you advise to me Some Advice Please...?

I feel incredible very difficulty expressing thoughts in English. I really do need a good level of English in order to get a promotion at work. But Even though I know how to say this one or another one the word, I can't to recall these words it when used in a different environment. I would be very foolish to look very foolish if during when conversing a conversation with the a foreign colleague. I will forget some the words. What can you advise to me? How can I improve my spoken English?

1. Be not afraid to speak up and make mistakes.  The more you are afraid, the more you will forget and more mistakes will be made. 

2.  Use short sentences and speak slowly.

3.  Ask them to correct you if there is a mistake.

4.  Like Amar advised, write often and get it corrected.  Learn why the corrections are such.  Learn to ask questions if you don't understand.  If you can write well, you can speak well, grammatically that is.  

5.  As for pronunciation and accent, all these depends on how well you perceive the sounds and how to reproduce them.  Watch more movies etc.